1. Field of the Invention
This invention relates generally to the processing of sludges, and more specifically to apparatuses and methods for removing VOCs from sludges.
2. Description of the Prior Art
Sludge is a muddy mass, deposit, or sediment of precipitated solid matter often produced by water and sewage treatment processes. Sludge may have a range of water contents and is often semi-fluidic. Sludge may be removed from tanks, ponds, lagoons, sumps, and other wet environments. Petroleum and industrial sludges often contain VOCs that are deemed to be hazardous, such as benzene, for example. When benzene is present in high concentrations, the sludge containing this VOC is classified as a RCRA hazardous waste. That is, Federal Regulations restrict treatment and disposal of such a sludge.
Removing VOCs from sludge or solids has been accomplished in a flare system which is similar to a soil burner. In these processes, VOCs, (including benzene), are removed by heating or cooking the solids in order to volatilize the VOCs. In this way, the VOCs are released in the form of gases. However, this method is expensive because large amounts of energy are required to heat the sludge. Furthermore, this process is not permitted in some localities. Even in locations where such processing is permitted by local authorities, governmental restrictions often push the cost of processing sludge too high. Therefore, the sludge from a certain part of the country is often shipped to a site in another part of the country where the heating process is tolerated. In this case, the cost of handling the sludge includes the cost of transporting it. Overall, the past processes of treating sludges are slow, inconvenient, and costly.
Another portion of the prior art deals with removal of VOCs from waste water. In recent years, stripping, and in particular air stripping, has become a popular way to process waste water. The use of air stripping has been used with increased frequency because it is relatively inexpensive, and because of newly developed devices that are somewhat portable and adjustable. The lower cost of running these air strippers is due in part to the fact that air stripping does not require the energy of heating that is required in steam stripping or distilling. On the other hand, air stripping, (and stripping overall), has been deficient in providing stripping of solids or semi-solids.
Steam strippers of the past are often used to remove ammonia from waste water. Distillation stripping is typically used to remove oil from waste water that is being treated. Each of these processes require rather specialized equipment and a large amount of energy. Steam and distillation strippers are deficient in providing a simple and inexpensive means for removing VOCs.
Overall, the prior art is deficient in the field of sludge processing in that there is a lack of a processes that are economical and simple. Specifically, the prior art is deficient in providing low energy costs due to the conventional heating and/or cooking processes for sludge materials.
The prior art devices and methods incorporate large semi-permanent equipment structures for processing solids on site. The prior art are thus deficient in providing methods for processing sludge that will obviate the need to ship sludge over large distances at high costs. In other words, the prior art does not adequately provide processes and apparatuses that permit sludges to be processed either on site or at nearby locations in order to remove VOCs from the sludge at lower costs.
The inadequacies of the prior art include the fact that the conventional methods for removing VOCs from sludge are very limited. There is a real deficiency in directly or indirectly removing VOCs in order to convert the sludge from a hazardous waste to a non-hazardous material or waste so that the sludge may be disposed of in areas of the country where disposal is not otherwise permitted.
Prior art methods for solids and sludge lack the greater efficiency associated with processing fluids as they move along a flow path. Furthermore, the prior art is deficient in providing a means for volatilizing solids as they move along a path during processing.
The prior art sytems for processing water are deficient for processing sludge because the prior art devices depend on flow of the substance being processed in the systems. In other words, there is a real lack of devices that can properly handle higher viscosity substances such as sludge. There is a related deficiency of pumps that are capable of pumping a substance that has a large percentage of solids. The prior art is also deficient in providing the system to include any preliminary steps to improve the subsequent conventional VOC removal from solids or sludges.